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MC34160 bảng dữ liệu(PDF) 6 Page - ON Semiconductor |
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MC34160 bảng dữ liệu(HTML) 6 Page - ON Semiconductor |
6 / 10 page MC34160, MC33160 http://onsemi.com 6 Comparators Three separate comparators are incorporated for voltage monitoring. Their outputs can provide diagnostic information to the microprocessor, preventing system malfunctions. The Reset Comparator Inverting Input is internally connected to the 2.6 V reference while the Noninverting Input monitors VO. The Reset Output is active low when VO falls approximately 180 mV below its regulated voltage. To prevent erratic operation when crossing the comparator threshold, 70 mV of hysteresis is provided. The Power Warning Comparator is typically used to detect an impending loss of system power. The Inverting Input is internally connected to the reference, fixing the threshold at 2.6 V. The input power source Vin is monitored by the Noninverting Input through the R1/R2 divider (Figure 11). This input features an adjustable 10 mA to 50 mA current sink IH that is programmed by the value selected for resistor RH. A default current of 6.5 mA is provided if RH is omitted. When the comparator input falls below 2.6 V, the current sink is activated. This produces hysteresis if Vin is monitored through a series resistor (R1). The comparator thresholds are defined as follows: R1 R2 1 + − IIB R1 Vth(lower) = Vref R1 R2 1 + + IH R1 Vth(upper) = Vref The nominal hysteresis current IH equals 1.2 V/RH (Figure 5). The Uncommitted Comparator can be used to synchronize the microprocessor with the ac line signal for timing functions, or for synchronous load switching. It can also be connected as a line loss detector as shown in Figure 12. The comparator contains 200 mV of hysteresis preventing erratic output behavior when crossing the input threshold. The Power Warning and Uncommitted Comparators each have a transistor base−emitter connected across their inputs. The base input normally connects to a voltage reference while the emitter input connects to the voltage to be monitored. The transistor limits the negative excursion on the emitter input to − 0.7 V below the base input by supply current from VCC. This clamp current will prevent forward biasing the IC substrate. Zener diodes are connected to the comparator inputs to enhance the ICs electrostatic discharge capability. Resistors R1 and Rin must limit the input current to a maximum of ±2.0 mA. Each comparator output consists of an open collector NPN transistor capable of sinking 2.0 mA with a saturation voltage less than 0.4 V, and standing off 40 V with minimal leakage. Internal bias for the Reset and Power Warning Comparators is derived from either VCC or the regulator output to ensure functionality when either is below nominal. Heat Tab Package The MC34160 is contained in a 16 lead plastic dual−in−line package in which the die is mounted on a special Heat Tab copper alloy lead frame. This tab consists of the four center ground pins that are specifically designed to improve thermal conduction from the die to the surrounding air. The pictorial in Figure 9 shows a simple but effective method of utilizing the printed circuit board medium as a heat dissipator by soldering these tabs to an adequate area of copper foil. This permits the use of standard board layout and mounting practices while having the ability to more than halve the junction to air thermal resistance. The example and graph are for a symmetrical layout on a single sided board with one ounce per square foot copper. = Sink Only Positive True Logic AC Line Line Sync. Power Warning Vref MPU Reset CO VO Uncommitted Comparator 4, 5, 12, 13 2.6 V Reference Thermal Shutdown Power Warning Vin R1 R2 2.6 V Rin Chip Disable Reset R .01 R IH On/Off Cin VCC 14 15 9 10 2 1 0.913 R 11 7 16 8 6 IH RH + + + + + − − − − − + + + Figure 11. Typical Microprocessor Application |
Số phần tương tự - MC34160_06 |
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Mô tả tương tự - MC34160_06 |
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